Emi-compatible mechanical temperature threshold sensor

ABSTRACT

A fluid temperature sensor may include a housing having an inlet, an indicator coupled to the housing, and a container disposed within the housing. The container may include a thermo-sensitive housing containing a thermal sensing element. The thermal sensing element may be configured to expand in response to reaching a threshold temperature thereby moving the container from a closed position to an open position. Fluid may flow through the inlet and fill the housing in the open position of the container to actuate the indicator into an activated position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.14/568,924, filed on Dec. 12, 2014, now issued as U.S. patent Ser. No.______, which claims priority to U.S. Provisional Patent Application No.61/919,522, filed Dec. 20, 2013, the contents of both of which arehereby incorporated in their entirety.

GOVERNMENT RIGHTS

This invention was made with government support under F34601-03-D-0006awarded by the United States Air Force. The government has certainrights in the invention.

FIELD OF TECHNOLOGY

The present disclosure relates generally to a mechanical temperaturesensor, and more particularly to temperature indicator for providing avisual indication of whether a substance has exceeded a thresholdtemperature.

BACKGROUND

It has become increasingly desirable to improve the overallconfiguration and operation of temperature sensors used for indicatingand detecting the presence of elevated temperatures. Temperature sensorsmay be designed for placement on the surface of an object, for example atemperature sensor utilizing irreversible temperature indicating paintthat changes to a specific color upon sensing a predetermined surfacetemperature. Other temperature sensors may require electronic supportingcontrol equipment for operation, such as sensors requiring an electricalmeasure device or voltage meter.

However, known temperature sensors are susceptible to electro-magneticinterference, incapable of reuse, and/or configured only to sensesurface or fluid temperatures.

Accordingly, overcoming these concerns would be desirable and could savethe industry substantial resources.

BRIEF DESCRIPTION OF THE DRAWINGS

While the claims are not limited to a specific illustration, anappreciation of the various aspects is best gained through a discussionof various examples thereof. Referring now to the drawings, exemplaryillustrations are shown in detail. Although the drawings represent theillustrations, the drawings are not necessarily to scale and certainfeatures may be exaggerated to better illustrate and explain aninnovative aspect of an example. Further, the exemplary illustrationsdescribed herein are not intended to be exhaustive or otherwise limitingor restricted to the precise form and configuration shown in thedrawings and disclosed in the following detailed description. Exemplaryillustrations are described in detail by referring to the drawings asfollows:

FIG. 1 illustrates a side view of a thermal sensor surface mountingconfiguration according to one example;

FIG. 2 illustrates a side view of a thermal sensor fluid mountingconfiguration according to one example;

FIG. 3A illustrates a side view of a thermal sensor piston configurationaccording to one implementation;

FIG. 3B illustrates a side cross-sectional view of a thermal sensorpiston configuration according to another implementation;

FIG. 4 illustrates a side view of a thermal sensor bellows configurationaccording to one example; and

FIGS. 5A and 5B illustrate a side cross-sectional view of a thermalsensor valve configuration, with FIG. 5A showing the thermal sensor in aclosed position and FIG. 5B showing the thermal sensor in an openposition.

DETAILED DESCRIPTION

Exemplary thermal sensors are described herein and illustrated in theattached drawings. While the thermal sensor may have variousimplementations, all may employ a phase-changing thermal sensing elementconfigured to expand upon reaching a temperature threshold and therebyapply pressure to move an actuator element or open a valve. As such, thethermal sensor herein described utilizes mechanics, rather thanelectronics, and therefore is impervious to electro-magneticinterference (EMI).

The thermal sensor may be used for indicating and detecting elevatedsurface and fluid temperatures in various aircraft, ship, automotive,locomotive, and facility engines (e.g., gas turbine engine). Forexample, the thermal sensor may be positioned in an oil line or drainplug of the engine to gauge the operating temperature of oil beingsupplied to the engine. Similarly, the thermal sensor may abut anactuator, valve, housing, or other surface of the engine to detect andindicate elevated temperatures. Accordingly, it may be easier to performmaintenance and detect malfunctioning or failing components due to thedeleterious effects high temperature may have on these components.However, although illustrative examples are described with respect toturbine engines, it is contemplated that the disclosure pertains toother components and/or designs, such as generators, power converters,transmissions, oil pressure pumps, etc.

FIG. 1 illustrates a surface sensor mounting configuration 100 accordingto one implementation. A thermal sensor 102 mounted to a surface 104according to one implementation. The thermal sensor 102 may include acontact member in thermal communication with the surface 104, forexample a combustor housing, generator, rectifier, converter, etc. Thethermal sensor 102 may be secured to the surface 104 via a mountingbracket 106 and fasteners 108. A high temperature gasket 110 may beplaced between the thermal sensor 102 and mounting bracket 106 matingsurfaces, forming a tight, thermally sensitive seal.

FIG. 2 illustrates a fluid sensor mounting configuration 200 accordingto one example. A thermal sensor 202 is mounted to detect thetemperature of a fluid 204. In one example, the thermal sensor 202 maybe located in a bore of a cavity 206 such that a contact member may bein thermal communication with the fluid 204 to be measured. A hightemperature gasket 208 may be disposed between the cavity and thethermal sensor mating surface to form a tight, thermally sensitive seal.Accordingly, the thermal sensor 102, 202 may be used for variousapplications for both surface and fluid detection of elevatedtemperatures.

Increased surface and/or fluid temperatures are detected and identifiedby the thermal sensor configured to activate an indicator at apredefined temperature threshold. That is, the thermal sensor mayinclude a thermal sensing element calibrated to trigger upon reachingthe temperature threshold, formed as a function of the actual surface orfluid temperature to be detected. If the thermal sensor, via the thermalsensing element, determines the surface or fluid temperature exceeds thethreshold, an indicator is activated and remains activated until manualreset. The thermal sensor, therefore, is completely reusable andindependent of an external energy source. In essence, the thermal sensoris entirely mechanical, thereby minimizing EMI interference withsurrounding equipment.

Referring to FIG. 3A, an exemplary thermal sensor 300 according to oneimplementation is illustrated. The thermal sensor 300 may include ahousing 302 having a thermal contact member 304 and an indicator 306coupled thereto. The housing may comprise a high temperature plastic,such as Nylon or polyether ether ketone (PEEK), or may comprise a metalsuch as stainless steel. The thermal contact member 304 may comprise ametal, such as stainless steel, brass, copper, or any other metalconfigured to facilitate thermal conduction from the surface/fluid to bemeasured. The thermal contact member 304 may be configured as a threadedbarrel, for example, having a generally flat bottom/base and acircumferential side surface.

The indicator 306 may be integrally formed with or coupled to thehousing 302, and may be comprised of a high temperature plastic, such asnylon or PEEK. According to one example, the indicator 306 may bedifferent in color to more easily distinguish from the housing 302.Additionally, the indicator 306 may be multi-colored to differentiatebetween activated and inactivated, thereby minimizing erroneous or falsetriggers that may lead to unnecessary replacement costs. For instance,the indicator 306 may include a bright colored stripe (e.g., red,orange, yellow) that may only be seen once the indicator 306 isactuated. The indicator 306 may resemble, for example, a button or thelike configured to activate or extend in position relative to thehousing 302 when actuated. The button indicator 306 may includeprotrusions about its periphery such that when actuated, the indicator306 remains in an activated or raised position until manually reset.Alternatively, the button indicator 306 may be threaded such thatactuation causes the button to unravel to an activated state, therebyrequiring manual twisting/screwing to reset the indicator 306.

FIG. 3B illustrates a cross-sectional view of the thermal sensor 300according to the example of FIG. 3A. The thermal contact member 304 maygenerally house and be in thermal communication with a thermal sensingelement 308. That is, the thermal contact member 304 may transfer heatfrom the surface/fluid to the thermal sensing element 308. Additionally,the thermal sensing element 308 may be disposed in a cup (not shown)configured to facilitate thermal conduction from the thermal contactmember 304 to the thermal sensing element 308. The thermal sensingelement 308 may generally be maintained within the thermal contactmember 304 and/or cup via an expandable diaphragm 322. The thermalsensing element 308 may comprise a hydrocarbon composition orthermostatic fluid configured to expand upon reaching a thresholdtemperature. None limiting examples of the thermal sensing element 308may include wax, alcohol, or any similar material configured to changephase (e.g., expand) at a given temperature. The thermal sensing element308 may be calibrated to change phase and expand at a desired indicationtemperature, for instance, by adjusting the hydrocarboncomposition/formulation to increase or decrease its tolerance to high orlow temperatures. Accordingly, the thermal sensing element 308 may beconfigured to detect a broad range of temperatures based on the materialcomposition.

The thermal sensing element 308 may be in communication with an actuatorelement 310. The actuator element 310 may be configured to actuate orotherwise activate the indicator 306 upon the expansion of the thermalsensing element 308. The actuator element 310 may comprise a unitarycomponent, such as a single piston 316, or may comprise multiplecomponents working in conjunction with one another. For example, theactuator element 310 may include a plug 312, a disk 314, and a piston316. The plug 312 may comprise a high temperature conical rubber orplastic, whereas the disk 314 may form the junction between the plug 312and the piston 316. The piston 316 may physically actuate the indicator306 in the activated state and comprise a high temperature material,such as rubber, plastic, or metal (e.g., stainless steel). The plug 312,disk 314, and piston 316 may be arranged axially in a guide 318 suchthat actuator moves monotonically or unitarily back in forth within thehousing 302.

The thermal sensor 300 may include a return member 320, such as a coilor spring. The return member 320 and thermal sensing element 308 may becalibrated such that the thermal sensing element 308 may overcome theresistance of the return member 320 during expansion in order to actuatethe indicator 306. The return member 320 may be arranged axially aroundthe actuator element 310 and/or guide 318, such that the actuatorelement 310 moves independently of the return member 320. The returnmember 320 may thus facilitate repositioning the thermal sensing element308 to its initial position (e.g., its position when cool) by exerting adownward force on the thermal sensing element 308. The return member 320may likewise exert a force on the indicator 306 to keep it in anactivated or extended position.

According to another implementation, the return member 320 may becoupled to the actuator element 310 (e.g., coupled to the piston 316)and engage the indicator 306 with the requisite force so as not tofalsely trigger the indicator 306 yet apply enough force to return theactuator element 310 to its initial position when the indicator 306 isreset after activation. That is, the return member 320 may not applyenough force to overcome the biasing force of the indicator 306independently without the additional force applied from the actuatorelement 310 in response to the expansion of the thermal sensing element308. Thus, the indicator 306 is only activated once the actuator element310 engages the indicator 306 via expansion of the thermal sensingelement 308.

During operation, the thermal sensor 300 detects and indicates elevatedsurface and/or fluid temperatures in an entirely mechanical process.When temperatures outside the thermal contact member 304 reach thecalibrated temperature threshold of the thermal sensing element 308, thethermal sensing element 308 begins to expand within the thermal contactmember 304 housing via the expandable diaphragm 322. This expansionconsequently forces the actuator element 310 upwards, thereby engagingthe indicator 306 and overcoming its biasing force to put the indicator306 in an activated position. The thermal sensing element 308 contractsas the external temperature decreases, however the indicator 306 remainsactivated in a raised position due to the protrusions and/or returnmember 320. That is, the return member 320 may exert force on theindicator 306 to keep the indicator 306 activated, and/or may facilitatethe repositioning of the thermal sensing element 308 as it contractsafter cooling. Accordingly, the indicator 306 may not only indicate thethreshold temperature has been detected, but may also act as a mechanismto manually reset the thermal sensor 300 during the next inspectionperformed by an operator. This, in turn, minimizes false or spuriousindications of elevated temperatures as the indicator 306 remainsactivated until manually reset upon inspection.

To reset the thermal sensor 300, the return member 320 appliesreciprocal force to return the actuator element 310 to its initialposition when the indicator 306 is reset (e.g., pushing, screwing, orotherwise resetting the indicator 306). The actuator element 310 in turnforces the thermal sensing element 308 to fully return to its initialposition so that the thermal sensor 300 is ready for reuse. As such, thedisclosed thermal sensor 300 indicates elevated external temperatures ina purely mechanical series of actions, and is therefore impervious toEMI radiation which may affect surrounding equipment. Equally, thethermal sensor 300 does not require batteries or an external powersource to function which may ultimately reduce costs and maintenancerequirements.

FIG. 4 illustrates a thermal sensor 400 according to anotherimplementation. The thermal sensor 400 according to FIG. 4 may includemany components similar to thermal sensor 300, including a housing 402,thermal contact member 404, indicator 406, thermal sensing element 408,and actuator element 410. Thermal sensor 400 may further include abellows member 412 made of high temperature material disposed within thehousing 402 configured to expand and contract along with the thermalsensing element 408. The thermal sensing element 308 may therefore becontained within the bellows member 412 and in thermal communicationwith the thermal contact member 404.

The bellows member 412, via the thermal sensing material 408, may beconfigured to actuate a further distance than generally necessary forthe thermal sensor 300 according to FIG. 3. Therefore, thermal sensor400 may provide more than an indication of whether a temperaturethreshold has been reached or otherwise triggered, but may also indicatethe duration of excessive temperatures and/or peak temperaturesdepending on the thermal sensing element 408 formulation. For instance,the thermal sensing element 408 may be configured to continue to expandfor the duration of measured high temperature, thereby actuating theindicator 406 beyond an initial indication. That is, the indicator 406may be designed such that the more distant the indicator 406 is actuatedsignifies sustained high temperatures or different degrees of hightemperature (e.g., the higher the temperature, the farther the indicator406 extends). The indicator 406 may include incremental protrusionswhich may keep the indicator 406 activated in a variety of positionseach of which is informative of measured external temperatures. Forexample, the indicator 406 may include a first stage of protrusions, asecond stage of protrusions arranged more distant than the first stagerelative to the housing, and so on, wherein each stage indicates atleast one of temperature exceeding the threshold (e.g., stage one is thethreshold temperature, stage two is the threshold temperature plus adefined degree Celsius) and/or a duration of extended high temperatures.

In operation, the thermal sensor 400 may proceed in the same manner asthermal sensor 300. For example, as temperatures outside the thermalcontact member 404 reach a temperature threshold, the hydrocarbonthermal sensing element 408 begins to expand within the bellows member412. The actuator element 410, which may be attached to or formed withthe bellows member 412, is forced upwards in the illustrated figure andengages the indicator 406 to activate the indicator 406. When theexternal temperature decreases, the thermal sensing element 408correspondingly contracts to its initial position, with the indicator406 remaining activated until manual reset. The thermal sensor 400 mayoptionally have a return member 414 which may exert a force on thebellows member 412 to ensure the thermal sensing element 408 is fullyreturned to its initial position upon manual reset of the indicator 406(e.g., when indicator 406 is pushed downward for resetting the thermalsensor 400). Upon resetting the indicator 406, the process of operationreturns to its original step and the thermal sensor 400 is thereforeeasily reusable for subsequent inspections.

FIGS. 5A and 5B illustrate a thermal sensor 500 valve configurationaccording to another exemplary implementation, with FIG. 5A showing thethermal sensor 500 in a closed position and FIG. 5B showing the thermalsensor 500 in an open position. The thermal sensor 500 may beparticularly advantageous to detect elevated fluid temperatures, as willbe discussed below. The thermal sensor 500 may include a housing 502, anindicator 504, and a thermal sensing element 506 arranged within thehousing 502. The housing 502, indicator 504, and thermal sensing elementmay generally resemble the materials and compositions detailed above.For example, the housing 502 may comprise a high temperature plastic ormetal, and the indicator 504 may include protrusion(s) 518 or mayunravel when activated. The thermal sensor 500, however, may not have athermal contact member, but rather may include an inlet or opening 508at the base of the housing for fluid to enter and subsequently heat upthe thermal sensing element 506.

The thermal sensing element 506 may be contained within a thermallyconductive container 510, for example comprising a metal such asstainless steel, brass, or copper. The container 510 may include aprojection 512 arranged about the perimeter. The projection 512 mayextend circumferential or otherwise around the perimeter of thecontainer 510 to form a seat and block the influx of fluid when thecontainer 510 is in a closed position. Thus, the projection 512 of thecontainer 510 may form the basis of the valve, blocking flow of fluid ina closed position and allowing the ingress of fluid in an open position.

The container 510 may include a bore which receives a support member514. The support member 514 may be arranged concentrically supportingthe thermal sensing element 506. That is, the support member 514 may beconfigured to maintain uniform and axial arrangement of the thermalsensing element 506 within the container 510. Additionally oralternatively, the support member 514 may provide support or act as ananchor for the thermal sensing element 506 to push off of as it expandswhen heated. For instance, the container 510 may include a deformableconical rubber plug (not shown) coupled to the end of the support member514. As the thermal sensing element 506 heats up and expands, thethermal sensing element 506 may push off of the plug and support member514 to move the valve in an open position. Thus, the container 510translates to an open position whereas the support member 514 remainsanchored at its designated position. Alternatively, the container 510may include a high temperature deformable rubber seal (not shown), suchas an O-ring, configured to act as a physical barrier to keep thethermal sensing element 506 from mixing with the high temperature fluid.Accordingly, as the thermal sensing element 506 expands within thecontainer, the O-ring may deform allowing the thermal sensing element506 to push off the support member 514 and move the container 510 intoan open position.

The thermal sensor 500 may further include a return member 516 arrangedwithin the housing 502 configured to reset the container 510 and thermalsensing element 506 to its initial closed position as the thermalsensing element 506 contracts due to decreased temperatures. The returnmember 516 may also act to prevent the valve from opening until thethreshold temperature is reached. Accordingly, the return member 516 maybe calibrated such that the expansion of the thermal sensing element 506generates enough force to overcome the biasing force in the returnelement 516 allowing the valve to open and fluid to flood in through theinlet 508.

In the initial closed position, the projection 512 abuts a correspondingengagement surface on the inner surface of the housing 502 to form aclosed valve position prohibiting the inflow of fluid into the housing502. As fluid temperatures reach the thermal threshold, the thermalsensing element 506 begins to expand and physically push off of thesupport member 514. The force exerted on the support member 514 by thethermal sensing element 506 must be greater than the resistance of thereturn member 516 to create a gap between the projection 512 and thehousing 502, thereby opening the valve. The subsequent inflow of fluidmay build pressure within the housing 502 which acts on the indicator504 and consequently activates in the indicator 504. The thermal sensingelement 506 may begin to contract as fluid temperatures decrease, andthe return member 516 may facilitate returning the container 510 to itsinitial closed position. Even after the container 510 returns to theclosed position, the indicator 504 may remain activated until manualreset due to protrusions arranged about the periphery of the indicator504.

Accordingly, the disclosed thermal sensor operates in a purelymechanical approach, and is thus impervious to EMI radiation and posesno risk of interfering with surrounding electronic equipment. Thethermal sensing element, such as a hydrocarbon composition or otherthermostatic fluid, may be formulated to expand at a desired temperaturethreshold and consequently actuate, via an actuating element, anindicator which remains activated until manually reset by an inspector.Therefore, the thermal sensor reduces false or spurious indications asthe indicator is configured to remain tripped in the activated stateuntil an external force is exerted on the indicator.

It will be appreciated that the aforementioned method and devices may bemodified to have some components and steps removed, or may haveadditional components and steps added, all of which are deemed to bewithin the spirit of the present disclosure. Even though the presentdisclosure has been described in detail with reference to specificembodiments, it will be appreciated that the various modifications andchanges can be made to these embodiments without departing from thescope of the present disclosure as set forth in the claims. Thespecification and the drawings are to be regarded as an illustrativethought instead of merely restrictive thought.

All terms used in the claims are intended to be given their broadestreasonable constructions and their ordinary meanings as understood bythose knowledgeable in the technologies described herein unless anexplicit indication to the contrary in made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary.

What is claimed is:
 1. A fluid temperature sensor, comprising: a housinghaving an inlet; an indicator coupled to the housing; a support membercoupled to the housing; a container disposed within the housing, thecontainer including a thermo-sensitive housing containing a thermalsensing element; wherein the thermal sensing element is configured toexpand in response to reaching a threshold temperature thereby movingthe container from a closed position to an open position; and whereinfluid flows through the inlet and fills the housing in the open positionof the container to actuate the indicator into an activated position. 2.The fluid temperature sensor of claim 1, further comprising a returnmember arranged between the container and the indicator for returningthe container to the closed position.
 3. The fluid temperature sensor ofclaim 1, wherein the indicator includes protrusions for securing theindicator in the activated position.
 4. The fluid temperature sensor ofclaim 1, wherein the container includes at least one of a conical rubberplug and a rubber seal, the at least one of the conical rubber plug andthe rubber seal configured to deform in response to expansion of thethermal sensing element.
 5. The fluid temperature sensor of claim 1,wherein the container further includes a bore for receiving the supportmember, wherein the support member is arranged concentrically within thethermal sensing element.
 6. The fluid temperature sensor of claim 5,wherein the support member is anchored to the housing and provides asupport for the thermal sensing element to push off and move thecontainer into the open position.
 7. The fluid temperature sensor ofclaim 1, wherein the container further includes a projection disposed ata perimeter of the container, the projection structured and arranged toengage an engagement surface of the housing.
 8. The fluid temperaturesensor of claim 7, wherein the projection extends circumferentiallyaround the perimeter of the container and blocks an influx of said fluidwhen the container is in the closed position.
 9. The fluid temperaturesensor of claim 1, wherein the thermal sensing element comprises ahydrocarbon material calibrated to expand at a predetermined temperaturethreshold.
 10. The fluid temperature sensor of claim 1, wherein thethermo-sensitive housing is a metal material.
 11. The fluid temperaturesensor of claim 10, wherein the metal material of the thermo-sensitivehousing includes stainless steel, brass, or copper.
 12. The fluidtemperature sensor of claim 1, wherein the indicator is configured toremain in the activated position until manually reset.
 13. A fluidtemperature sensor, comprising: a housing having an inlet; an indicatorcoupled to the housing; a thermally conductive container, the thermallyconductive container including a projection extending circumferentiallyabout a perimeter of the thermally conductive container structured andarranged to engage an engagement surface on an inner surface of thehousing; a thermal sensing element arranged within the thermallyconductive container; wherein the thermal sensing element is expandablein response to reaching a threshold temperature thereby moving thethermally conductive container from a closed position to an openposition; and wherein fluid flows through the inlet and fills thehousing in the open position of the thermally conductive container toactuate the indicator in an activated position.
 14. The fluidtemperature sensor of claim 13, further comprising a support membercoupled to the housing and arranged concentrically in the thermalsensing element, wherein the support member is configured to maintainuniform and axial arrangement of the thermal sensing element in thehousing.
 15. The fluid temperature sensor of claim 14, wherein thethermally conductive container includes a bore for receiving the supportmember, wherein the support member is anchored to the housing betweenthe inlet and the thermally conductive container.
 16. The fluidtemperature sensor of claim 13, further comprising a return memberarranged between the thermally conductive container and the indicatorfor returning the thermally conductive container to the closed position.17. The fluid temperature sensor of claim 16, wherein the return memberhas a resistance less than a reciprocal force of the thermal sensingelement.
 18. A method of sensing a temperature, comprising: receiving afluid in a housing via an inlet; exposing a thermally conductivecontainer arranged in the housing to the fluid, wherein the thermallyconductive container is in thermal communication with a thermal sensingelement, the thermal sensing element expandable in response to apredetermined threshold temperature; actuating an indicator in responseto reaching the predetermined threshold temperature, wherein expansionof the thermal sensing element moves the thermally conductive containerfrom a closed position to an open position such that the fluid fills thehousing in the open position and forces the indictor into an activatedposition.
 19. The method of claim 18, wherein the indicator remains inthe activated position until manually reset.
 20. The method of claim 18,further comprising returning the thermally conductive container to theclosed position via a return member, wherein the return member has aresistance less than a reciprocal force of the thermal sensing element.